Action Potential (session 5) Flashcards Preview

Semester 1-ICPP > Action Potential (session 5) > Flashcards

Flashcards in Action Potential (session 5) Deck (36):
1

What does the action potential depend on?

Ionic gradients
Relative permeability of the membrane

2

What is the action potential?

Change in voltage across the membrane

3

True or false: the action potential is propagated with loss of amplitude

FALSE - there is no loss of amplitude

4

True or false: depolarisation to threshold initiates an action potential at the axon hillock

TRUE

5

What is the driving force?

Difference between membrane potential and equilibrium potential

6

Complete the sentence:

If the conductance (g) to any ion is increased, the membrane potential (Vm) will move ______ to the equilibrium potential for that ion.

Closer

7

What is the conductance of the membrane to a particular ion dependent on?

The number of channels for that ion that are open

8

True or false: sodium equilibrium potential dictates the generation of an action potential

TRUE

9

True or false: not many ions need to flow for an AP to be initiated

TRUE

10

What is capacitance?

Ability to store charge

11

True or false: the Na+/K+ ATPase pump is needed for repolarisation

FALSE

12

What do voltage-clamps allow?

Membrane currents to be measured at a set membrane potential

13

What is the absolute refractory period?

Nearly all Na+ channels are in their inactivated state and no matter how strong the stimulus is, no AP is initiated

14

What is the relative refractory period?

Na+ channels are recovering from inactivation, excitability returns towards normal as number of channels in the inactivated state decreases. If there is a strong stimulus, another AP may be initiated

15

How many alpha subunits does the functional channel of a voltage gated Na+ channel have?

One

16

How many alpha subunits does the functional channel of a voltage gated K+ channel have?

Four

17

True or false: voltage gated K+ channel is 1/4 the size of a Na+ channel

TRUE - 4 subunits are needed to make a functional K+ channel

18

True or false: channels open and close in a random manner

TRUE

19

How do local anaesthetics work?

By blocking Na+ channels (no AP)

20

Give an example of a local anaesthetic

Procaine

21

In what order do local anaesthetics block axons?

1. Small myelinated axons
2. Unmyelinated axons
3. Large myelinated axons

22

Complete the sentence:

Injection of current into an axon will cause the resulting charge to spread along the axon and cause an _________ _____ ______ in the membrane potential.

Immediate local change

23

What does membrane resistance depend on?

Number of ion channels open

24

Complete the sentence:

The lower the resistance, the _____ ion channels are open.

More

25

Complete the sentence:

A high capacitance leads to the voltage changing more ______ in response to current injection

Slowly

26

Complete the sentence:

High resistance leads to a change in voltage spreading ________ along the axon

Further

27

Complete the sentence:

The wider the axon, the ______ and _______ the conductance of the AP

Faster
Further

28

Schwann cells are in which nervous system? And what is the equivalent in the other nervous system?

PNS
Oligodendrocytes

29

Is there a high or low density of Na+ channels at the nodes of Ranvier?

High

30

What is saltatory conduction?

Action potential 'jumping' from node to node, allowing a much faster conduction velocity

31

True or false: AP occurs only at nodes

TRUE

32

How does the myelin sheath improve conduction? (4)

1. Large increase in membrane resistance (Rm)
2. Large decrease in membrane capacitance (Cm)
3. The above increase length constant
4. Slight decrease in time constant

33

Name some diseases that affect the conduction of the AP in the CNS and briefly describe which nerves they affect (2)

1. Multiple sclerosis - affects all CNS nerves
2. Devic's disease - optic and spinal cord nerves only

34

Which diseases affect the conduction of APs in the PNS? (2)

1. Landry-Guillain-Barre syndrome
2. Charcot-Marie-Tooth disease

35

Diseases affecting the conduction of the AP result from the breakdown or damage of what?

The myelin sheath

36

Complete the sentence:

In regions of demyelination, the density of the action current is reduced because of _________ and ___________ ________

Resistive
Capacitance shunting